With the increased practice of preventative healthcare to help reduce costs worldwide, sensor technology improvement is vital to patient care. Point-of-care diagnostics can reduce time and lower labor in testing, and also can effectively avoid transporting costs because of portable designs.
Microfabrication and nanotechnology allows for interfacing fabricated components directly with biological and chemical elements in new ways, creating opportunities for new devices. One example of this is biosensor devices. In the most general sense, a biosensor is a device that can detect, measure and/or report the presence of specific components in biological samples. An example of a biosensor is a glucose sensor used by people to monitor and control diabetes. By detecting different biological components, biosensors can be used for numerous applications in healthcare and diagnostics. The ability to test for a specific biomarker can help stop diseases such as cancer while they are still localized. This makes them easier and cheaper to cure. While there are technologies in existence that can perform such tasks, they often require samples to be tested at a laboratory dedicated to this purpose. Both transporting and testing the sample can be expensive and time-consuming, making a point-of-care design ideal in terms of time and money.
Many of these devices can take advantage of microfabricated components to allow for accurate and sensitive detection of components in biological samples. One example of these includes microfabricated electrodes, which can be used for electrical detection of biomolecules. Though designs of biosensor electrodes can vary, a common design uses interdigitated electrodes (IDEs)
Various bio-sensing techniques have been proposed using optical, electrical, and mechanical detection methods. Although individual methods can vary, electrical and electrochemical biosensors work by measuring changes in electrical properties caused by the presence of specific biological targets. These changes may be caused by interference in electric fields, chemical reactions, or from conductive labels. Electrodes are used as interfaces both in applying electric fields to the tested samples and as a method of transmitting and measuring electrical detection signals. The types of measured electrical signal vary as well depending on the application, and may be simple impedance or resistance measurements, capacitance measurements, or electrical spectroscopy, taking measurements over a range of frequencies.
Compared to optical methods of detection, impedance tests are easier to use and more versatile. The equipment often required for optical detection is too large, complex, and expensive for portable point-of-care testing. However, optical methods tend to achieve high sensitivity, which is why they are commonly used. Mechanical methods, on the other hand, can yield specific and sensitive results, but they are much more prone to inaccuracies due to temperature and pH changes.
Impedance based detection methods have been shown to have a lower maximum sensitivity than other techniques. In addition, some techniques that use interdigitated electrodes to detect a target employ a broad frequency range impedance spectroscopy to detect the target. The results of the impedance spectroscopy are often fitted to a model of the interdigitated electrode/nanoparticle system. The broad frequency range impedance spectroscopy and/or model fitting typically require appropriate electronics or other computer related components, which add to the size and expense of the systems.
Accordingly, improvements in impedance based detection methods and devices are desired.
The above information is presented as background information only to assist with an understanding of the present disclosure. No assertion or admission is made as to whether any of the above might be applicable as prior art with regard to the present disclosure.